Cisco 300-540 Exam With Confidence Using Practice Dumps

In a cloud-scale or data center–scale environment,Virtual Extensible LAN (VXLAN)is used as anoverlay technologyto transportLayer 2 segments over a Layer 3 underlay network. VXLAN encapsulates Layer 2 Ethernet frames inside UDP/IP packets, allowing broadcast, unknown unicast, and multicast (BUM) traffic and tenant Layer 2 domains to be extended across a routed IP fabric.

Key points aligned with Cisco Service Provider Cloud Infrastructure design principles:

VXLAN creates aLayer 2 overlay on top of a Layer 3 underlay.

TheVXLAN Network Identifier (VNI)provides a much larger segmentation space than traditional VLANs, enabling multi-tenancy at cloud scale.

Because the underlay is pure Layer 3 (IP routed fabric), VXLAN allows you tointerconnect Layer 2 segments between leaf switches or data centers over an IP/MPLS backbonewithout relying on large Layer 2 domains in the physical network.

Why the options evaluate as follows:

Option A: extends Layer 2 segments across the underlying Layer 3 infrastructure✅This is the core benefit of VXLAN in cloud-scale designs. VXLAN encapsulates Layer 2 frames intoIP/UDP headers, allowing isolated Layer 2 segments (per VNI) to be stretched across a routed IP network. This enables:

Multi-tenant Layer 2 connectivity across a distributed cloud fabric

Mobility of virtual machines or containers while keeping same IP/MAC addressing

Use of an IP-based leaf–spine or service provider underlay for scalability and resiliency

Option B: extends Layer 3 segments across the underlying Layer 2 infrastructure❌This is the opposite of what VXLAN does. VXLAN is explicitlyL2-over-L3, not L3-over-L2. Extending pure Layer 3 segments over Layer 2 is not the VXLAN use case.

Option C: reduces spanning-tree complexity across the Layer 2 infrastructure⚠️(Partially related but not the primary or direct benefit)In modern designs, the underlay isLayer 3 routed, and VXLAN overlays provide logical Layer 2 segments. This designavoids dependence on spanning tree in the fabric, whichindirectlyreduces STP complexity. However, the fundamental, exam-relevant benefit isL2 extension over L3, so C is not the best or most accurate answer compared to A.

Option D: eliminates the need for a Layer 3 underlay in the service provider infrastructure❌VXLAN absolutelyrequiresan IP (Layer 3) underlay for transport. VXLAN tunnels are built over a routed infrastructure (leaf–spine, MPLS/IP core, etc.). It does not remove the need for Layer 3; it depends on it.

Comprehensive and Detailed Explanation

For distancesgreater than 20 miles, valid inter-facility transport options must support:

Metro-scale connectivity

High bandwidth

Low latency

Carrier-grade reliability

Acarrier access Ethernet ring (MEN / Metro Ethernet)is designed for:

Interconnecting data centers or meet-me rooms

Distances far exceeding 20 miles

High-availability layer-2 or layer-3 transport

Why the others are invalid:

CAT6e→ maximum ~100 meters

Multimode fiber→ typically <2 km (~1.25 miles)

Private wireless→ not used for high-capacity DC interconnects, unreliable for core transport

Thus, the only correct carrier-grade method isCarrier access Ethernet ring.

In Cisco data center and cloud-scale designs, adouble-sided vPC(also called vPC-to-vPC) is used when both ends of a Layer 2 port channel are formed by a pair of switches that operate as vPC peers. In this model:

On the aggregation or leaf side, two switches (in this case,LEAF1 and LEAF2) form a vPC domain with a vPC peer-link and keepalive.

On the access or ToR side, two switches (in this case,TOR1 and TOR2) must also form their ownvPC domainwith a peer-link and vPC keepalive.

The port-channel that interconnects the two vPC domains is then configured as a vPC on both sides, creating a vPC-to-vPC topology.

The problem statement specifies thatLEAF1 and LEAF2 are already configured as vPC peers. For a double-sided vPC to work, the other side (TOR1 and TOR2) must also behave as a single logical entity for the downstream Cisco UCS server and for the upstream vPC connection towards LEAF1 and LEAF2. This is only achieved when TOR1 and TOR2 are configured as vPC peers with:

A vPC domain ID

A vPC peer-link between TOR1 and TOR2

vPC member port-channels towards LEAF1 and LEAF2 and towards the Cisco UCS server

Therefore, the next required step is to configure avPC between TOR1 and TOR2.

Evaluation of the options:

Option A, “Add all the switches to the fabric,” is generic and not specific to vPC configuration. It does not address the technical requirement to form a vPC domain on the ToR side.

Option B, “Configure peering between LEAF1 and LEAF2 and TOR1 and TOR2,” is incorrect because vPC peering is only configured between the two switches that form each vPC domain (LEAF1–LEAF2 and TOR1–TOR2), not across all four switches together.

Option C, “Configure MSTP between TOR1 and TOR2,” is not required for establishing a double-sided vPC. vPC designs rely on the vPC control plane and the peer-link, not on spanning-tree between the vPC peers for normal operation.

Option D, “Configure a vPC between TOR1 and TOR2,” correctly describes configuring TOR1 and TOR2 as a vPC pair (vPC domain with peer-link), which is the mandatory step to create a double-sided vPC topology with LEAF1 and LEAF2.